A father from Watford who lied to try to protect his police officer son by taking the blame for hurling racial abuse at neighbours has failed in a bid to clear his name.

Mohammed Riaz claimed he had made offensive remarks to his next-door neighbours, with whom he had an 'unfortunate and longstanding dispute', after his son, Shahban Riaz, was arrested.

But Shahban Riaz was found guilty of racially aggravated harassment at Luton Magistrates Court and his father was convicted of attempting to pervert the course of justice.

Riaz senior, 58, of Langley Way, was fined £500 and ordered to pay another £500 towards the cost of his prosecution at St Albans Crown Court in October last year.

Yesterday, he challenged his conviction at London's Criminal Appeal Court, with his lawyers arguing it was "unsafe" because of flaws in the trial process.

But his appeal was dismissed by three of the country's top judges, who upheld the conviction.

The court heard the father and son were standing in their front garden when their neighbours returned home one evening in October 2010 and heard racially abusive comments made about them.

They contacted police and Shahban Riaz was arrested and charged later that month.

Fearing Shahban may lose his job as a police officer if convicted, his father then made a statement claiming he was the one who had uttered the offensive words.

But his account was not believed and he too was arrested, in January 2011, on suspicion of trying to pervert the course of justice.

At his trial, the jury was told his son had been convicted, but were instructed they had to be sure Shahban, and not his father, was responsible for the abuse.

They also heard evidence from the neighbours' phone call to report the matter to police, in which the son was identified as the person who had made the remarks.

Mohammed Riaz's lawyers argued his conviction was "unsafe" because of the fact the jury were told that his son had already been found guilty of making the racist comments.

They also said the details of the phone call should have been disclosed to the defence at an earlier stage of the trial.

But, dismissing his appeal, Lord Justice Davis said the trial judge's instructions to the jury meant they effectively had to consider the case against Shahban afresh, which was "favourable" to his father's defence.

Sitting with Mr Justice Nicol and Judge Elgan Edwards QC, he added: "The trial judge's change of stance meant the jury had to find Shahban committed the acts as well.

"This might seem to have been a very fortunate outcome to the defence, which might explain why they never sought to have the jury discharged."